Poul Anderson, who has died aged 74 from prostate cancer, published his first short story in Astounding Science Fiction magazine in 1947, and went on to produce more than 100 books, most of them novels. One of the last writers from science fiction's golden age, he was in the generation that followed authors like Isaac Asimov, Robert Heinlein and Frederik Pohl.

The late SF author James Blish, who called Anderson "the enduring explosion" because of his seemingly endless productivity, described his novel Tau Zero (1970) as "the ultimate hard science-fiction novel". Recently reissued in Britain as a classic Gollancz yellow jacket, it follows the ramifications of relativity theory to a startling conclusion, when a spaceship accelerates to the speed of light, causing an ever-widening disparity between external, and on-board, time.

Anderson's first novel, Brain Wave (1954), is regarded as one of his greatest; the solar system moves out of a force field which, for millennia, has been suppressing intelligence, and suddenly mankind and all animals become hyper-intelligent. The Boat Of A Million Years (1989) deals with a different change to a much smaller group of people: eight immortals who are dissatisfied with the way history is moving.

In the great tradition of SF, many of Anderson's tales are linked in a loose "future history" in three main sequences, featuring the fat and boisterous interstellar merchant prince Nicholas van Rijn, the sophisticated and tough agent of the Terran empire, Dominic Flandry, and the Psychotechnic League stories about man's expansion out from the solar system into the galaxy.

Born to Danish parents in Bristol, Pennsylvania, Anderson graduated in physics from the University of Minnesota in 1948. His Scandinavian heritage and scientific training are evident throughout his work.

In a 1997 interview with the SF magazine Locus, Anderson said: "So much American science fiction is parochial - not as true now as it was years ago - but the assumption is of one culture in the future, more or less like ours, with the same ideals and the same notions of how to do things, just bigger and flashier technology. Well, you know darn well it doesn't work that way." Indeed, his descriptive writing was often poetic, sometimes lush.

For Sir Arthur C Clarke, Anderson was one of science fiction's giants, though he was as well known for his fantasy novels and his rewritings of myth as for his sometimes outrageous humour. The best example of this is his delightful short novel The Makeshift Rocket (1962), about an engineer who escapes a hostile planet in a spaceship made of beer kegs and powered by "hot agitated beer".

With Gordon R Dickson, who died in January, Anderson wrote several novels about the Hoka, teddy bear-like aliens who imitate human pop-culture, but who are unable to understand metaphor and allusion, taking it as factual - thus providing the authors with endless opportunities for puns and farce.

As a creative fantasy writer, his classics included The Broken Sword (1954), Three Hearts And Three Lions (1961) and A Midsummer Tempest (1974). The first is a dark tale based on Norse mythology, with two changeling half-brothers, one chivalrous and one cruel, who battle to a mutually destructive end.

The second is a splendid story of a man flung back in time to a world of Carolingian myth, of knights, damsels and dragons. The third is set in an alternate world where Shakespeare plays, particularly A Midsummer Night's Dream and The Tempest, really happen - the first chapter heading reads "Thunder and lightning. A heath about to be blasted." The war between the Cavaliers and Cromwell's Puritans includes observation balloons and steam trains, with Oberon and Titania joining King Arthur to fight against the industrial revolution.

In some later works, particularly the King Of Ys historical fantasies of the late 1980s, Anderson collaborated with his wife Karen, whom he married in 1953. He also used a number of pseudonyms.

Sometimes criticised as rightwing, he described himself as "an 18th-century liberal", in the American libertarian sense. "As for the value of the individual, I'm quite consciously in the Heinleinian tradition there," he said in the Locus interview. "It's partly an emotional matter - a libertarian predilection, a prejudice in favour of individual freedom - and partly an intellectual distrust based on looking at the historical record . . . a distrust of large, encompassing systems."

His many science fiction awards included seven Hugo Awards and three Nebula Awards. President of the Science Fiction Writers of America (1972-73), he won the SFWA's Grandmaster Award in 1997, and was inducted into the Science Fiction and Fantasy Hall of Fame last year. Last month, he won the John W Campbell Memorial Award for his novel Genesis (2000).

He is survived by his wife and daughter.

Poul William Anderson, writer, born November 25 1926; died July 31 2001